There is an interesting story told in the Book of Judges, Chapter 17.
A certain woman left her fortune to her son Michiyahu for the purpose of setting up an idolatorous cult. He had a fancy idol and a temple built for this purpose, but could not find a priest to lead the services. Then into town rode one Yehonasan ben Gershom ben Menashe, of the House of Levi. Michiyahu recognized suitable charismatic qualities in this stranger, and offered him the job of High Priest of his new religion. At first Yehonasan refused, but then Michiyahu reviewed the cult’s finances with him, and he agreed.
Who was this man Yehonasan of the House of Levi?
His grandfather could not have been Menashe, our well-known villain, since he had not been born yet. According to the Gemara (Bava Batra 109) “Menashe” is really a disguised form of “Moshe”, so he was actually the grandson of Moshe Rabbeinu! What did Moshe do to get a grandson like that?
The Baal HaTurim quotes a Midrash that after Moshe went to work as a shepherd for Yisro, the high priest of Midian, he sought his permission to marry his daughter Tsipora. Yisro agreed, but negotiated that Moshe’s firstborn son would be dedicated to serve as a priest in the Midianite religion. Moshe agreed, calculating that by the time his firstborn son would be old enough to serve as a priest, he (Moshe) would have converted Yisro to Judaism, so that Yisro would no longer hold him to his undertaking.
As it turned out, Moshe’s calculation proved correct, so that his eldest son Gershom was indeed saved from idol-worship.
Nevertheless, says the Midrash, Moshe was punished for this behavior by the fact that Gershom’s son became the high priest of a pagan cult. Now what exactly was Moshe’s sin here? I claim it was very serious — a confusion of one’s own role with G-d’s.
This position (apart from being sinful) is also logically incoherent — in order to bring the word of G-d to as many people as possible, he had to break the word of G-d! This was also the sin of Moshe.
Perhaps, with his prophetic vision, he could foresee that Tsipora was destined for him. Perhaps he could foresee that he would convert Yisro to Judaism in time, so that his firstborn son Gershom was not really running any risk of idolatory.
But this is all irrelevant.
His response to Yisro’s condition should simply have been: “No way! I cannot even consider such a condition for a son of mine!” If Tsipora was destined for him, well and good — he would still marry her, one way or another. (Maybe Yisro would have backed down from his condition!) And if not, not. In the end, Moshe was punished for this. Although his son Gershom did not become an idol-worshiper, his grandson, Gershom’s son, did.
Let us remember to do only our own work, and leave G-d’s work to G-d.